The present invention relates generally to keypads for electronic devices, particularly hand-held electronic devices such as mobile telephones, palmtop computers, personal digital assistants (PDA's), or the like, and more specifically, to a multi-tier keypad assembly for such electronic devices.
Electronic devices, particularly hand-held electronic devices such as mobile telephones, palmtop computers, personal digital assistants (PDA's), and the like, comprise a class of devices typically requiring an operator to input information via a keypad, such as a numeric keypad, a small alphanumeric keypad, or the like. The keypad may be used for entering alphanumeric text and common commands, selecting menus to be displayed by a display, or the like. The keypad generally includes a set of keys contacting domes disposed over a circuit board. As the keys are pressed, they deform or compress the domes, providing input to the circuit board and tactile feedback to the operator of the electronic device. The amount of tactile feedback provided by the keys is described by the bounce performance of the keypad.
The trend toward miniaturization of electronic devices creates the need for smaller keypads. Further, the increasing complexity of operations required by such electronic devices creates the need for keypads having more keys, including keys having specialized characters and/or functionality. However, as more keys are packaged in smaller spaces, the keys become more concentrated or dense and the distances between the keys decrease, limiting the potential size of domes for providing tactile feedback when a key is pressed and reducing bounce performance. Moreover, a greater concentration of keys may hinder an operator from easily pressing a desired key, as the spaces between the keys become smaller than the width of a typical human fingertip.
Consequently, it would be desirable to provide a keypad having a high key density without loss of mechanical bounce performance. Further, it would be desirable to provide a keypad having multiple sets of keys which are differentiable from one another by adjusting the height of one or more of the sets of keys when keys of that set are to be used.